1. Field of Invention
The present invention relates to a structure of a color liquid crystal display (LCD) and a method of producing the same. More particularly, the present invention relates to a method of utilizing color photoresist to form black matrix and spacers on a control circuit substrate and the LCD structure fabricated by the same method.
2. Description of Related Art
Liquid crystal is a material having properties between those of crystal and liquid. The alignment of the liquid crystal molecules varies with external stimulation such as an electrical field generated by an applied voltage. Hence, this feature of the liquid crystal molecules can be utilized to create a display unit.
Liquid crystal material was discovered in 1888, and applications thereof first appeared in 1963. However, the value of the commercial application was not proved until Sharp in Japan developed a liquid crystal display applied in a calculator. Japanese companies have continued to develop the technology and improve the product""s function. Development and improvement have made the liquid crystal display widely applicable.
Liquid crystal display (LCD) has many advantages over other conventional types of displays including high display quality, small volume occupation, light weight, low voltage drive and low power consumption. Hence, LCDs are widely used in small portable televisions, mobile telephones, video recording units, notebook computers, desktop monitors, projector televisions and so on. Therefore, the LCD has gradually replaced the conventional cathode ray tube (CRT) as a mainstream display unit. In particular, the thin film transistor (TFT) LCD has the lion""s share of the market for its high display quality.
The color filter on array (COA) technique is the most common in color TFT LCD production. Black matrix, which separates pixels, is located on the color filter and which prevents photo current, is located on the TFTs, and spacers on the metal lines are usually made of black resin. The black matrix and the spacers are usually formed after the color photoresist and the pixel electrodes are formed. The black resin of the photoresist type is patterned by photolithography. However, the light transmittance and sensitivity of the photoresist-type black resin is very poor. Therefore, the exposure time has to be increased to obtain ideal patterns, and the throughput of the stepper is seriously affected.
It is therefore an objective of the present invention to provide a method of utilizing color photoresist to form black matrix and spacers on a control circuit substrate.
It is another objective of the present invention to provide a LCD structure fabricated by the same method of utilizing color photoresist to form black matrix and spacers on a control circuit substrate.
In accordance with the foregoing and other objectives of the present invention, a method of utilizing color photoresist to form black matrix and spacers on a control circuit substrate Is provided. A control circuit, made of control devices and a chessboard-like circuit, is formed on the control circuit substrate. The chessboard-like circuit has first openings, second openings, third openings and supporting areas, and the control devices are formed on corners of the first, the second and the third openings, respectively. The method comprises the following steps. A first-color photoresist is formed on the control circuit substrate, and then the first-color photoresist is patterned to form first-color filters on the first openings, the control devices and the supporting areas, respectively, and form contact windows in the first-color filters is to expose electrodes of the control devices, respectively. A second-color photoresist is formed on the control circuit substrate, and then the second-color photoresist is patterned to form second-color filters on the second openings and the supporting areas, respectively. A third-color photoresist is formed on the control circuit substrate, and then the third-color photoresist is patterned to form third-color filters on the third openings and the supporting areas, respectively. A first transparent conductive layer is formed on the control circuit substrate. Next, the first transparent conductive layer is patterned to form pixel electrodes on the first openings, the second openings, the third openings and partial areas of the control devices, and the pixel electrodes electrically connect to the electrodes of the control devices through the contact windows, respectively. A fourth-color photoresist is formed on the control circuit substrate, and then the fourth-color photoresist is patterned to form fourth-color filters on the supporting areas and the control devices, respectively.
According to a preferred embodiment, the first-color photoresist, the second-color photoresist, the third-color photoresist and the fourth-color photoresist are red-color photoresist, green-color photoresist, blue-color photoresist and blue-color photoresist, respectively, or blue-color photoresist, green-color photoresist, red-color photoresist and red-color photoresist, respectively. The method of patterning the first-color photoresist, the second-color photoresist, the third-color photoresist and the fourth-color photoresist comprises photolithography.
In accordance with the foregoing and other objectives of the present invention, a color liquid crystal display is provided. The color liquid crystal display comprises a first transparent substrate, a control circuit on the first transparent substrate, first-color filters, second-color filters, third-color filters, pixel electrodes, fourth-color filters, a second transparent substrate, a common electrode, and a liquid crystal layer. The control circuit, comprises of control devices and a chessboard-like circuit, is on the first transparent substrate. The chessboard-like circuit has first openings, second openings, third openings and supporting areas, and the control devices are located on corners of the first, the second and the third openings, respectively. The first-color filters are located on the first openings, the control devices and the supporting areas, respectively, and each of the first-color filters located on the control devices has a contact window to expose electrodes of the control devices, respectively. The second-color filters are located on the second openings and the supporting areas, respectively. The third-color filters are located on the third openings and the supporting areas, respectively. The pixel electrodes are located on the first openings, the second openings, the third openings and partial areas of the control devices, and the pixel electrodes electrically connect to the electrodes of the control devices through the contact windows, respectively. The fourth-color filters are located on the supporting areas and the control devices, respectively, whereby the first-color filters, the second-color filters, the third-color filters and the fourth-color filters on the supporting areas are stacked to form spacers. The common electrode is on a surface, which faces the first transparent substrate, of the second transparent substrate. The liquid crystal layer is located between the first and the second transparent substrates.
According to a preferred embodiment, the first-color photoresist, the second-color photoresist, the third-color photoresist and the fourth-color photoresist are red-color photoresist, green-color photoresist, blue-color photoresist and blue-color photoresist, respectively, or blue-color photoresist, green-color photoresist, red-color photoresist and red-color photoresist, respectively.
In conclusion, the invention utilizes the lack of overlap between the light transmittance wave bands of the red-photoresist and the blue-photoresist. Hence, the black matrix is formed on the control devices only by the red-photoresist and the blue-photoresist to avoid photocurrent occurring during the xe2x80x9coffxe2x80x9d state of the control devices. Moreover, the invention allows the spacers to be formed by stacking four layers of color filters of the color of the red, green, blue, and blue or the blue, green, red, and red on the supporting areas on the metal lines. Since the light transmittance and sensitivity of the color photoresists are much better than those of the black resin, the exposure time can be greatly reduced to increase the throughput of the stepper.
It is to be understood that both the foregoing general description and the following detailed description are by examples, and are intended to provide further explanation of the invention as claimed.